Big cities are noted for giving their residents a feeling of anonymity. Such anonymity has been found to reduce the constraints against antisocial behavior, and it seems probable that it would also reduce the pressures toward prosocial behavior. Thus, feelings of anonymity may help to explain the fact that, in large cities, bystanders often fail to help the victim of an emergency. At present, there appears to be no research that directly tests this supposition. The research proposed here is designed to test the effect of bystander anonymity on helping in an emergency situation, as a function of the sex of the bystander. Procedures analogous to those that have been used to show the effect of anonymity on antisocial behavior will be employed, with helping, rather than aggression, as the dependent measure.